Is Welding Certification Needed in this Case? 1

[Mike4321]

My company makes a fitting that has three welds. Two of the welds are fairly standard and we have certified PQR's and WPS's to cover them.

In the fitting there is a 1/16-27 NPTF threaded hole. This is used to fill the interior with an inert gas while welding and after the first two welds are done a plug is put into this hole. The top of the plug is welded to the fitting to ensure it doesn't twist back out in any way at all. This weld has a very small penetration (maybe a thousandth of an inch) and is more of a safety precaution.

We have a company interested in the fittings, but they want to see all our certifications, work instructions, etc

My question is does this weld fall under ASME BPVC Section 8? The weld is on the pressure boundary, but isn't for containment.

The threaded plug is in conformance (but not certified)with ASME B31.3B section 314.2, would you think that this enough?

 

[Mike4321]

Sorry, I forgot to add any comments or suggestions would be greatly appreciated.

 

[grayseal]

Mike4321,

My interpretation of Section VIII is that if you weld on the pressure containing part of a vessel, the material must be allowed by Section II and the weld must be made per a qualified WPS.

grayseal

 

[Mike4321]

I just realized I put Section 8, when I meant Section 9 - Welding and Brazing Qualifications. I want to know if a PQR and WPS will be necessary for this weld even though its a safety precaution and does not assist in pressure containment.

Thanks

 

[bmoorthy]

What ever may be the purpose or the size, so long as the welding is done on any pressure containing part, WPS supported by appropriate PQR is required.

The case you have presented is similar to tack welds. As per ASME and ANSI even temporary tack welds which are made on pressure parts are required to be supported by WPS/PQR.

It appears that you are providing the tack weld so as to prevent the plug from un locking. Why don't you try avoiding tack weld. Just damage the last thread by punching the ends of thread in the female side so that the plug is fixed there and cannot un lock it self. Or why don't you provide spring washer which prevents plugs from opening itself. Or try avoiding the opening totally by modifying the joints/WPS of the main welds. If the fittings are CS fittings back purging is generally not required for GTAW welds. Alternatively use of deep penetration electrodes such as E6010 would do with a skilled SMAW welder. For exotic material or for SS back purging is required.

You may even crimp the pluged area by providing a taper zone thus locking the plug.

 

[deanc]

Need more info. What Code are the fittings built to? Is the seal weld performed after the final pressure test? Have you talked to your AIA? Is this a common practice?

There may be a way around this. However,it is always good practice to have a qualified procedure.

 

[Mike4321]

The fittings are built to ASME B31.3. The fitting is pressure tested after the final weld. I haven't been able to talk to my AI yet, he's very hard to get a hold of.

I figured it would be necessary I just wanted to be certain. Does anyone have any useful links about qualifying tack welds?

When welding two pieces of different thickness two PQR's are required, one for each thickness, correct? What is the best way to treat the weld itself because its penetration is only a very small way into the base metals?

Thanks

 

[leanne]

I have written & qualified a WPS for a one-time welding application. I no longer have access to the ASME codes since I'm not doing that job any more so I cannot quote chapter/section info from the code for why we did a procedure qualification for WPS to perform a single weld.

 

[deanc]

You could do this with 1 PQR. Test with a thick to thin. Review Article II of SecIX and look at Essential Varibles.

Tack welds,full welds-makes no difference. Qualifies the same.

Talk to your AI about doing this seal weld after the pressure test. There are some Code Interps.

 

[quadswift]

We have in the past use purge needles for this kind of thing on nuclear submarine and nuclear reprocessing pipework construction in awkward situations.

You can purge through the root / fit-up of the second weld (taped) whilst you weld the first one if practical.

If not purge through each weld root / fit-up using the needle.

Fix a hypodermic type needle to the end of the inert gas hose and introduce it into the root gap of the weld.

Tape the rest of the weld (and the other weld fit-up if necessary).
Allow sufficient time for purging and check the dew-point by opening the tape overlap or punching a pinhole in the tape and sniffing.

Remove a part of the tape at the overlap and start welding the root whilst continuing to purge. Continue welding and removing the tape as you go. You are maintaining the purge pressure.
At the last moment, remove the needle and finish the root weld.

Doing this, you could save yourself money from not drilling / tapping / buying plugs and you could get that sale!
Make sure needles and tape are of suitable contact materials for the materials to be welded.
Regards,
Quadswift